Hollow turbine bucket and method of manufacturing same



Nov.'25, 1,516,607

J.JOHANSON HOLLOW TURBINE BUCKET AND METHOD OF MANUFACTURING SAME Filed July 30, 1925 Inventor: John Johanson,

- Hisw t' or eg- 20 with such buckets has been to provide a Patented Nov. 25, 1924. V

'NITED STATES r 1,516,607 PATENT OFFICE.

JOHN JOHANSON, OT SGHENEOTADY, NEW YORK, ASSIGN OR TO GENERAL ELECTRIC I COMPANY, A CORPORATION OF NEW YORK.

' nor-now rumamn BUcxE'r Arm marnon or MANUFACTURING sum.

Application filed Iuly 80, 1928. Serial No. 654,528.

To all whom it may concern:

Be it known that 1, JOHN JOHANSON, a citizen of the United States, residing at Schenectad in the county of Schenectady, State of Nie w York, have invented certain new and useful Improvements in Hollow Turbine Buckets and Methods of Manufacturing Same, of which the following is a specification.

It has heretofore been proposed to make turbine buckets hollow in order to reduce their weight and thereby decrease the centrifugal stresses but even with hollow buckets of light wei ht the centrifugalstresses become of consi erable value asthe buckets increase in length. The stresses" are-highest of course, at the roots of the buckets and gradually decrease toward the tips, the greatest stress being in the basesof the buckets. One of the problems in connection practical structure having su'fiicient strength at its base or inner end to withstand the centrifugal stresses met with in modern turbine practice and the object of my invention is to provide an improved hollow turbine bucket structure which will meet this condition and an improved method of manufacturing thesame.

For a consideration of what believe to be novel and my invention, attention is dirooted to the accompanying description and the claims appended thereto.

In the drawing, Fig. 1 is a. view of a partially completed tur ine bucket embodying my invention; Fig. 2 is a vertical sectional view thereof; Fig. 3 is a sectional lan view through the base of the bucket; ig. 41s an exploded view of the parts used in manufacturmglmy improved bucket, and Fig. 5 is a view s owing a completed bucket mounted on a rotor. Y

The front and back Walls of the bucket may be formed of two curved pieces of sheet metal suitably united along their edges, 6 being the front wall and 7 the back wall. I may with advantage form. walls 6 and 7 from Monel metal and they ma lie-united rspective along their edges in any suita 1e manner such as by sol ering, brazing, welding or the like. The back wall 7 extends throughout the length of the bucket while the front wall terminates at the top of the base. The

base is made up primarily of two main pieces, a front piece 8 and a back piece 9.

The front piece 8 has a curved surface 10 which fits the inner surface of back wall 7 and the back piece 9 has a curved surface 11 which fits around the outer surface of wall 7. The lower end of wall 7 is thus held between'the two base pieces 8 and 9. The front base piece 8 has a which projects up between wal s 6 and 7 and thls projecting portion is preferably tapered in accordance with the falling off of the centrifugal stresses. This may be done by cutting a V-shaped notch in the projection as indicated at 13. The projection 12 forms a reinforcing member for giving strength to the inner end of the bucket.

ortion 12 In constructing a bucket embodying my invention'I take a front and back wall 6 and 7 which have been suitably united to each other along their edges and put the front base piece 8 in position as best shown in Figs. 1 and 2, slipping the reinforcing projection 12 up between walls 6- and 7. I then put back wall piece 9 in position around the lower end of back wall 7 and fasten the parts together in what may be termed an initial or temporary manner by means of pins 14 which may be driven into holes 15. Or, the parts may be fastened in any other suitable manner. When thusassembled the lower edge of inner wall 6 takes 7 against the flat top surface of base piece 8. I then apply to such to surfacea holding plate 16 which may be astened in position temporarily by any suitable means such as by means of the pin- 17.

After the parts have been this assembled- I then unite themto form-a unitary struc ,parts and eflect a. union of them, forming" in substance a unitary structure.

' After the assembled parts have been thus united into a unitary structure, the base may be finished to any suitable contour for attachmg it to a rotor or bucket-carrying member. In Fig. 5 I have shown it provided with slots 18 to form a dove-tail for engagement with a groove 19 in the rotor this being a well-known form of bucket fastening means. In Fig. 5, the rotor or bucket carrying member is indicated at 19. Preferably, pins 14 are so located that when the bucket bases are finished, the pins are removed with the waste material. The holes 15 and pins 14 do not therefore serve in any way to weaken the structure. The 'plate' 16 serves to grip and hold the lower end of inner wall 6. The base member 9 preferabl extends up along the back of wall 7 as indicated at 20 to brace the back of the bucket.

lhe bucket may be provided with a suitable tenon 21 for fastening in place a bucket cover 22, the tenon being fixed to the'bucket by welding or. in any other desired manner.

By the above described arrangement 'I provide a structure wherein the bucket proper comprisin walls 6 and 7 is firmly anchored to the ase and also a structure wherein the base and the portion of the bucket next to the base are amply strong to withstand the centrifugal stresses met with. At the same time by following m method of construction the bucket may". e manufactured at a reasonable cost. The reinforcing projection 12 may be made as long as found desirable in any particular case and may be given a crosssection such as to provide the desired strength. By its use I provide in substance the equivalent of a tapered bucket. I 1

What I claim as new and desire to secure by Letters Patent of the United States, is

1. A turbine bucket comprising curved front and back walls united along their longitudinal edges, the back wall projecting below the front wall at one end, and a plurality of base pieces between which the projecting end of the back wall is held.

2. A turbine bucket comprising curved front and back walls united along their longitudinal edges, the back wall projecting below the front wall at one end, a front and back base piece between which the projecting end is clamped, and a reinforcing projection on'the front base piece which extends up between said front andback walls.

3. A turbine bucket comprising curved front and back walls united along their longitudinal edges, the back wall projecting below the front wall at one end, a front and back base piece between which the projecting end is clamped, and a tapered reinforcing member which projects from the base piece up between said front and back walls.

4. A turbine bucket comprising curved front and back walls united along their longitudinal edges, and base pieces between which the lower ends of said walls are held, said wallsv and base pieces being united by fused metal.

5. A turbine bucket comprising curved 7 front and back walls united along their longitudinal edges, and a plurality of base pieces between which the lower end of the back wall is held, said wall and back piece being united by fused metal.

6. A turbine bucket comprising curved JOHN JOHANSON. 

